Microwave

Group 1 Thermodynamic Project: Microwave

History:
http://www.gallawa.com/microtech/history.html

• Dr. Percy Spencer noticed something very unusual during a radar-related research project. He was testing a new vacuum tube called a magnetron
  when he discovered that the candy bar in his pocket had melted. Dr. Spencer another experiment but this time he placed some popcorn kernels near the tube and he watched the popcorn sputtered, cracked and popped all over his lab.
• These primitive units where gigantic and enormously expensive, standing 5 1/2 feet tall, weighing over 750 pounds, and costing about $5000 each.

On September 18, 1999, Dr. Percy LaBaron Spencer was inducted into the National Inventors Hall of Fame and took his place in history alongside such great inventors as Thomas Edison, the Wright Brothers and George Washington Carver.





How Do They Work??
http://www.gallawa.com/microtech/how_work.html

• Microwaves are an output of microwave energy (get out!) and the system is divided into two sections
  • control section
    • consists of timer, system to control power output, protection devices
  • high voltage section
    • high voltage transformer, special diode, capacitor arrangement
• electricity travels through the power cord into the microwave
• when door is closed a circuit is complete
• "control circuit" sends a signal to high-voltage transformer, which changes the voltage from 115 to 3000 volts
• energy is transmitted in "waveguide" which puts energy in cooking area
• stirring blades or rotating antenna evenly disperse heat to foo
• when timer goes off or door is opened, the energy stops just like a light switch

What forms of energy are involved and how it relates to thermodynamics
SOURCE:http://encyclopedia2.thefreedictionary.com/Microwave+energy

• The microwave process is an exothermic reaction that uses electrical energy to power the appliance and electromagnetic energy called microwaves and thermal energy heat the objects inside of the appliance.
• The microwave process is exothermic because the electromagnetic energy and the thermal energy give off heat that heat is absorbed by the object, like food that you would be heating in the microwave. The two forms of energy cause the liquid-like substances in the food, like water and fat to heat up.
• Heat is transferred from the microwave to whatever is inside of the appliance.
• The enthalpy for a microwave is negative, it has a positive entropy value
• Microwave Energy:Portion of the electromagnetic spectrum that is situated between radio waves and infrared radiation. Microwaves have wavelengths ranging from 30 cm to 1 mm, corresponding to frequencies from about 1 gigahertz (109 Hz) to 1 terahertz (1012 Hz).